H influenzae Flashcards
What does H influenzae require for growth in lab?
H. influenzae requires blood-derived factors for growth in the lab
hemin (factor X) and/or NAD (factor V) (released when blood is boiled in lab)
Facts about the H influenzae bacteria
Gram neg rod. encapsulated (six types: A, B, C, D, E, F) and non encapsulated. Pili or fimbrae; IgA protease; OMP (outer membrane protein), LOS (lipooligosaccharide - shorter than LPS); CM, PG, OM. No exotoxin
What do Neisseria meningitidis, Haemophilus influenzae, Streptococcus pneumoniae, Neisseria gonorrheae have in common?
IgA protease (cleaves IgA in mucous membranes) and capsule.
Pathogenesis and transmission of H influenzae
Droplet or contact; adhere ia pili/OMP to nasal pharynx. No capsule: spread on mucous surface to middle ear (infection!), sinus, or lower; capsule: into blood stream in 5 minutes, resist phagocytosis. Both release LOS.
How can non encapsulated H influenzae cause meningitis?
Usually cannot invade blood stream. Often directly from ear or sinus
Tx for H influenzae?
Must cross the blood brain barrier, and because it’s a serious infection - IV. 3rd gen cephalosporin
HIB vaccine?
Used to be polysaccharide (T independent response). Now add conjugate (protein that you’ve seen before) and can get a stronger B cell response (present protein to TH cell and stimulate B cell)
What can HIB cause? Tx?
Epiglottitis. Swells and blocks the airway. toxic, often drooling, sitting in a tripod position with their chin protruding (to protect their airway). May have a “hot potato” voice. Need intubation and antibiotics.
Non-typeable HI
Not as invasive. Causes otitis media (the other cause is S pneumonia)
Review of HI infections
Meningitis: HIB; Otitis and sinusitis: non-typeable HI; Bacteremia, Epiglottitis: HIB; pneumonia: HIB and nt HI.
